[llvm] [NFC][TableGen] DirectiveEmitter code cleanup (PR #107775)

[Rahul Joshi via llvm-commits]

jurahul wrote:

> Thank you for the cleanup. Now, is there any way you could separate the `{}->()` conversions with the rest? A `{}->()` conversion can have a surprising effect like `std::vector<int> Vec(3,5)` vs `std::vector Vec{3, 5}`, so I would have to be more careful and understand each type's constructor than, say, when reviewing comments or removal of `llvm::`.

I may be, though all the {} -> () changes are for constructors with single arguments here, and for classes defined in the DirectiveEmitter.h, so the risk of the issues you mentioned above is less. But I can if you insist.

https://github.com/llvm/llvm-project/pull/107775